1. Field of the Invention
This invention relates to a method of and a system for measuring the glucose concentration in an organism, and more particularly to a method of and a system for noninvasively measuring the glucose concentration in aqueous humor in an anterior chamber.
2. Description of the Related Art
Though the mean level of the glucose concentration in the blood varies from person to person, it is an important indication on the basis of which whether a diabetic is to be dosed is determined.
The blood glucose concentration largely varies in a very short time according to the kind of meal and/or physical activities or due to concurrence of diseases. An emergency dosing is often required due to abrupt increase of the blood glucose concentration.
Accordingly, it is desired that the blood glucose concentration of the patient be monitored at as short intervals as possible. Conventionally, the blood glucose concentration has been generally monitored by cutting the tip of a finger of the patient and analyzing the blood thus collected. Accordingly because of pain accompanying cutting the finger, it is difficult to force the patient to be subjected to measurement of the blood glucose concentration a plurality of times a day.
Recently there have been proposed noninvasive methods of measuring the blood glucose concentration instead of an invasive method having such drawback.
The noninvasive methods mainly involve noninvasive measurement of the glucose concentration in aqueous humor in the anterior chamber between the cornea and the lens of the human eyeball. The glucose concentration in aqueous humor in the anterior chamber has a close relation with the blood glucose concentration though the relation varies from person to person.
In one of such noninvasive methods, the glucose concentration is determined on the basis of optical rotation of infrared rays entering the aqueous humor in an anterior chamber as disclosed, for instance, in Japanese Unexamined Patent Publication No. 51(1976)-75498 (corresponding to U.S. Pat. No. 3,958,560). In another method, Raman scattering light by glucose is measured as disclosed, for instance, in PCT Japanese Publication No. 6(1994)-503245. In still another method, optical properties of light reflected by the lens is measured as disclosed, for instance, in Japanese Unexamined Patent Publication No. 6(1994)-237898.
We have proposed a noninvasive method of measuring the glucose concentration in aqueous humor in an anterior chamber in Japanese Unexamined Patent Publication No. 9(1997)-299333 in which a plurality of laser beams or the like different in wavelength band are caused to enter the eyeball, intensity of backscattering light from an interface between the cornea and the aqueous humor in the anterior chamber and intensity of backscattering light from an interface between the aqueous humor in the anterior chamber and the lens are accurately detected by wavelength band, for instance, by light heterodyne measurement, absorption properties of the aqueous humor for the respective wavelength bands are obtained on the basis of the backscattering light intensities and the like and the glucose concentration in the aqueous humor is obtained by near-infrared spectrometry including multivariate analysis on the basis of the absorption properties of the aqueous humor for the respective wavelength bands. Further we have proposed a noninvasive method of measuring the glucose concentration in aqueous humor in an anterior chamber in Japanese Patent Application No. 9(1997)-358101 in which the glucose concentration in the aqueous humor is determined on the basis of the refractive index of the aqueous humor in the anterior chamber which is determined on the basis of intensity or the like of reflected light from the anterior chamber, the refractive index of the aqueous humor in the anterior chamber having a very close relation with the glucose concentration in the aqueous humor.
In the systems where light is caused to enter the eyeball, it is necessary to suppress influence of the light on the eyeball as low as possible, and especially in the case where the light is a laser beam, the intensity of the laser beam must be carefully controlled.
However, in any of the above identified patent publications, there is no disclosure on a means for controlling the intensity of the laser beam to be entered in the eyeball.